Sacha Baron Cohen's Borat made pranking Americans look like shooting fish in a barrel; Brüno targets the same barrel, but this time the fish have got a little wiser. This is essentially the same movie as its predecessor with a different comic persona, but where Borat's charming naivety caught Americans with their guard down, Brüno's screaming campness often raises their defences.

In addition, people now know who Baron Cohen is and how he works. As a result it looks like they've had to work harder to get the material.

The smash-and-grab public stunts are noticeably shorter - there's sadly nothing to match Borat's astounding naked wrestling scene, though there is something similar. And the "story" linking them together is even flimsier.

Brüno is fired from his Austrian television fashion show Funkyzeit after hijacking a show with his new Velcro jumpsuit, and so heads to the US to become "the most famous Austrian since Hitler".

As you'd expect, Brüno charges, or rather minces, into some of the least advisable situations imaginable - attempting to seduce a confused Republican congressman Ron Paul, telling a gayness-curing evangelist he has "blowjob lips", parading through an ultra-orthodox area of Jerusalem in Hasidic-inspired hotpants (if there's one thing Brüno does that Borat can't, it's costume).

And again, he lures the unsuspecting into shameful acts - getting Latoya Jackson to eat sushi off a naked Mexican gardener, for example (a scene later cut when Latoya's brother Michael died), or gaining showbiz moms' consent to dress their children as Nazis.

Beneath the idiocy, Baron Cohen is also a politically astute agent who's devised an ingenious way to confront and expose serious social issues - and indulge his own exhibitionism.

Brüno is funniest, though, when it's at its most politically incorrect, especially when it comes to homosexuality. There's an eye-popping montage of extreme gay sex practices (imaginary, one hopes), a surfeit of waving penises, dildos, fetish gear, anal bleaching, and an excruciating mime in which Brüno fellates the ghost of a deceased member of Milli Vanilli in front of a psychic.

Much of it is unavoidably hilarious, but is he lampooning homophobia or perpetuating it?

Either way, he gets away with a great deal simply by being a brilliant physical comedian. That should stand him in good stead.

His star has risen to such an extent, it's unlikely he'll be able to make this type of undercover comedy again. Nor will he need to.

• This article was amended on 13 July 2009. The original review referred to the initial version of Bruno released before Michael Jackson's death, a version with a scene involving Latoya Jackson. This has been clarified.